Catalysts for para-ethyltoluene dehydrogenation

Abstract

Para-ethyltoluene dehydrogenation catalyst compositions and processes for using such catalysts are provided. The catalyst compositions comprise a catalytically active iron compound, e.g., iron oxide; a potassium catalyst promoter, e.g., potassium carbonate; an optional chromium compound stabilizer, e.g., chromic oxide, and a gallium compound, e.g., gallium trioxide. Utilization of particular amounts of gallium compound in dehydrogenation catalyst compositions of this type will provide a catalyst especially suitable for promoting the selective dehydrogenation of para-ethyltoluene to form para-methylstyrene with sustained catalyst activity, with minimized aromatic ring loss and with minimal formation of popcorn polymer from the reaction effluent.

What is claimed is: 
     
       1. A process for the dehydrogenation of para-ethyltoluene to selectively form para-methylstyrene, said process comprising contacting a feed comprising para-ethyltoluene and steam under steam dehydrogenation reaction conditions with a catalyst composition comprising: a. from about 30% to 60% by weight of iron oxide, calculated as ferric oxide;   b. from about 13% to 48% by weight of potassium compound, calculated as potassium oxide;   c. from about 0% to about 5% of chromium compound, calculated as chromic oxide; and   d. from about 1% to 15% by weight of a gallium compound, calculated as gallium trioxide.   
     
     
       2. A process for the dehydrogenation of para-ethyltoluene to selectively form para-methylstyrene, said process comprising contacting a feed comprising para-ethyltoluene and steam with a catalyst composition comprising: a. from about 30% to 60% by weight of iron oxide, calculated as ferric oxide;   b. from about 13% to 48% by weight of potassium compound, calculated as potassium oxide;   c. from about 0% to about 5% of chromium compound, calculated as chromic oxide; and   d. from about 1% to 15% by weight of a gallium compound, calculated as gallium trioxide;   said contacting occurring under steam dehydrogenation conditions which include a temperature of from about 500° C. to 700° C., a liquid hourly space velocity for para-ethyltoluene of from about 0.3 to 3 and a steam to hydrocarbon ratio in said feed of about 1:1 to 5:1.   
     
     
       3. A process in accordance with claim 2 wherein a. the iron oxide comprises from about 35% to 55% by weight of the catalyst composition;   b. the potassium compound comprises from about 27% to 41% by weight of the catalyst composition;   c. the chromium compound comprises from about 1% to 4% by weight of the catalyst composition; and   d. the gallium compound comprises from about 2% to 10% by weight of the catalyst composition.   
     
     
       4. A process in accordance with claim 3 wherein the weight ratio of steam to para-ethyltoluene in the feed ranges from about 1.5:1 to 4:1. 
     
     
       5. A process in accordance with claim 2 wherein said catalyst composition additionally contains up to about 20% by weight of a binder/filler component selected from the group consisting of portland cement, calcium aluminate, sawdust, carbon, wood flour, graphite, methylcellulose and mixtures thereof.